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Abstract

An antireflecting micro-structured interface, working in the resonance domain, and made from a bi-periodic array of semi-spherical hollowing-out in a silicon substrate is presented. Its parameters such as sphere radius and position of sphere centers from the surface are optimized numerically. A simple and robust process is described allowing such kind of antireflective surfaces to be fabricated for the infrared range. Spectral and angular reflectance measurement demonstrates the efficiency of the antireflective micro-structured interface which can easily be adapted for the visible range and for photovoltaic applications by a simple homothetic modification of the micro-structure typical dimensions.

Figures (6)

Fig. 1 (a) Sketch of the structure of interest: a silicon substrate in which spheres have been pulled out bi-periodically at the surface. Period = 3 µm. The sphere radius and the position of sphere centers from the surface are the two parameters which can be adjusted to obtain the most efficient antireflective effect. (b) Sketch of the elementary pattern of the structure which is repeated bi-periodically at the surface.

Fig. 2 Computed reflectance value mappings (in %) in normal incidence as a function of the sphere radius (horizontal axis) and the position of sphere centers from the surface (“offset” on the vertical axis). The period value is fixed at 3 µm and the wavelengths are respectively 3µm, 4 µm and 5 µm for Fig. 2(a), Fig. 2(b) and Fig. 2(c).

Fig. 3 (a) Spectral reflectance values of the structure having a sphere radius = 0.88µm and a position of the sphere centers from the surface = −0.25µm, in normal incidence. (b) Spectral reflectance values of the structure having a sphere radius = 0.96µm and a position of the sphere centers from the surface = −0.25µm, in normal incidence.